summarylogtreecommitdiffstats
path: root/0005-x86-Fix-early-boot-crash-on-gcc-10-next-try.patch
diff options
context:
space:
mode:
Diffstat (limited to '0005-x86-Fix-early-boot-crash-on-gcc-10-next-try.patch')
-rw-r--r--0005-x86-Fix-early-boot-crash-on-gcc-10-next-try.patch131
1 files changed, 0 insertions, 131 deletions
diff --git a/0005-x86-Fix-early-boot-crash-on-gcc-10-next-try.patch b/0005-x86-Fix-early-boot-crash-on-gcc-10-next-try.patch
deleted file mode 100644
index ee7b469fb8d..00000000000
--- a/0005-x86-Fix-early-boot-crash-on-gcc-10-next-try.patch
+++ /dev/null
@@ -1,131 +0,0 @@
-From 53e90d763b7fe8bec6a0c86b6813131cd8e25026 Mon Sep 17 00:00:00 2001
-From: Borislav Petkov <bp@suse.de>
-Date: Wed, 22 Apr 2020 18:11:30 +0200
-Subject: [PATCH 5/6] x86: Fix early boot crash on gcc-10, next try
-MIME-Version: 1.0
-Content-Type: text/plain; charset=UTF-8
-Content-Transfer-Encoding: 8bit
-
-... or the odyssey of trying to disable the stack protector for the
-function which generates the stack canary value.
-
-The whole story started with Sergei reporting a boot crash with a kernel
-built with gcc-10:
-
- Kernel panic — not syncing: stack-protector: Kernel stack is corrupted in: start_secondary
- CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.6.0-rc5—00235—gfffb08b37df9 #139
- Hardware name: Gigabyte Technology Co., Ltd. To be filled by O.E.M./H77M—D3H, BIOS F12 11/14/2013
- Call Trace:
- dump_stack
- panic
- ? start_secondary
- __stack_chk_fail
- start_secondary
- secondary_startup_64
- -—-[ end Kernel panic — not syncing: stack—protector: Kernel stack is corrupted in: start_secondary
-
-This happens because gcc-10 tail-call optimizes the last function call
-in start_secondary() - cpu_startup_entry() - and thus emits a stack
-canary check which fails because the canary value changes after the
-boot_init_stack_canary() call.
-
-To fix that, the initial attempt was to mark the one function which
-generates the stack canary with:
-
- __attribute__((optimize("-fno-stack-protector"))) ... start_secondary(void *unused)
-
-however, using the optimize attribute doesn't work cumulatively
-as the attribute does not add to but rather replaces previously
-supplied optimization options - roughly all -fxxx options.
-
-The key one among them being -fno-omit-frame-pointer and thus leading to
-not present frame pointer - frame pointer which the kernel needs.
-
-The next attempt to prevent compilers from tail-call optimizing
-the last function call cpu_startup_entry(), shy of carving out
-start_secondary() into a separate compilation unit and building it with
--fno-stack-protector, is this one.
-
-The current solution is short and sweet, and reportedly, is supported by
-both compilers so let's see how far we'll get this time.
-
-Reported-by: Sergei Trofimovich <slyfox@gentoo.org>
-Signed-off-by: Borislav Petkov <bp@suse.de>
-Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
-Reviewed-by: Kees Cook <keescook@chromium.org>
-Link: https://lkml.kernel.org/r/20200314164451.346497-1-slyfox@gentoo.org
----
- arch/x86/include/asm/stackprotector.h | 7 ++++++-
- arch/x86/kernel/smpboot.c | 8 ++++++++
- arch/x86/xen/smp_pv.c | 1 +
- include/linux/compiler.h | 6 ++++++
- 4 files changed, 21 insertions(+), 1 deletion(-)
-
-diff --git a/arch/x86/include/asm/stackprotector.h b/arch/x86/include/asm/stackprotector.h
-index 91e29b6a86a5..9804a7957f4e 100644
---- a/arch/x86/include/asm/stackprotector.h
-+++ b/arch/x86/include/asm/stackprotector.h
-@@ -55,8 +55,13 @@
- /*
- * Initialize the stackprotector canary value.
- *
-- * NOTE: this must only be called from functions that never return,
-+ * NOTE: this must only be called from functions that never return
- * and it must always be inlined.
-+ *
-+ * In addition, it should be called from a compilation unit for which
-+ * stack protector is disabled. Alternatively, the caller should not end
-+ * with a function call which gets tail-call optimized as that would
-+ * lead to checking a modified canary value.
- */
- static __always_inline void boot_init_stack_canary(void)
- {
-diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
-index 69881b2d446c..9674321ce3a3 100644
---- a/arch/x86/kernel/smpboot.c
-+++ b/arch/x86/kernel/smpboot.c
-@@ -262,6 +262,14 @@ static void notrace start_secondary(void *unused)
-
- wmb();
- cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
-+
-+ /*
-+ * Prevent tail call to cpu_startup_entry() because the stack protector
-+ * guard has been changed a couple of function calls up, in
-+ * boot_init_stack_canary() and must not be checked before tail calling
-+ * another function.
-+ */
-+ prevent_tail_call_optimization();
- }
-
- /**
-diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c
-index 802ee5bba66c..0cebe5db691d 100644
---- a/arch/x86/xen/smp_pv.c
-+++ b/arch/x86/xen/smp_pv.c
-@@ -92,6 +92,7 @@ asmlinkage __visible void cpu_bringup_and_idle(void)
- cpu_bringup();
- boot_init_stack_canary();
- cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
-+ prevent_tail_call_optimization();
- }
-
- void xen_smp_intr_free_pv(unsigned int cpu)
-diff --git a/include/linux/compiler.h b/include/linux/compiler.h
-index 034b0a644efc..732754d96039 100644
---- a/include/linux/compiler.h
-+++ b/include/linux/compiler.h
-@@ -356,4 +356,10 @@ static inline void *offset_to_ptr(const int *off)
- /* &a[0] degrades to a pointer: a different type from an array */
- #define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
-
-+/*
-+ * This is needed in functions which generate the stack canary, see
-+ * arch/x86/kernel/smpboot.c::start_secondary() for an example.
-+ */
-+#define prevent_tail_call_optimization() asm("")
-+
- #endif /* __LINUX_COMPILER_H */
---
-2.26.2
-